Field of the Invention
The present invention relates to a technique for inspecting a semiconductor device or a photo device.
Description of the Background Art
There is already known a semiconductor inspecting device which detects an electromagnetic wave emitted from a semiconductor device when irradiating it with pulsed laser light, thereby to inspect the semiconductor device in non-contact (Japanese Patent Application Laid-Open No. 2010-60317).
Further, the present applicant has proposed a technique of irradiating a photo device with pulsed light and detecting an electromagnetic wave emitted from the photo device accordingly, thereby to inspect the photo device (Japanese Patent Application Laid-Open No. 2013-19861).
Moreover, there has already been proposed a technique of scanning with probe light the inside of a region irradiated with pump light by using pump-probe measurement to make photoexcited carriers visible (“Study of Carrier Dynamics in LT-GaAs Photoconductive Switch Using Pump-Probe Laser Terahertz Emission Microscope”, Shogo Fujiwara, et al., IEICE Technical Report. ED 110(342), 87-90, 2010-12-09). Specifically, it is described that by using a photoconductive switch being a representative terahertz wave generating device as a sample, dynamics of photoexcited carriers are observed at a subpicosecond temporal resolution and a several-micrometer spatial resolution.
Inspecting the processes of generation, movement and disappearance of the photoexcited carriers on the subpicosecond level in the semiconductor device or the photo device gives extremely precious information in inspecting performance or a defect of those. In particular, in the photo device, analyzing generation of the photoexcited carriers, the lifetime thereof after the generation to recombination, movement thereof to the electrode, and the like can give extremely important information in evaluating performance or a defect of the photo device. However, a technique of detecting the dynamics of the photoexcited carriers in the photo device is unknown.
Moreover, in the report by Fujiwara et al., only the inside of the region irradiated with the pump light is irradiated with the probe light. There has thus been a problem of not being able to inspect photoexcited carriers which are generated, move or disappear out of the region with the pump light.